I’ve mapped nearly all of Baltimore’s bus routes and there are lots of cases I can think of offhand where the bus uses the parking lot roads to alight passengers directly at a business, often even with a signed stop. This is common at Walmart. You could make a case that the route the bus takes is often the ring road around (but within) a parking lot and therefore not tag that particular way as a parking_aisle, such as the yellow highlighted ways in the graphic below.
I’ve also added local university shuttle buses’ routes and they do frequent places like parking lots. I’d tend to vote against removal of service subcategories solely based on the presence of a bus route relation.